Power recovery from catalytic conversion systems employing fluidized solids



w p 1943- H. K. WHEELER, JR 2,449,096

POWER RECOVERY FROM CATALYTIC CONVERSION SYSTEMS EMPLQYING FLUIDIZEDSOLIDS Original Filed larch 29. 1945 Z 33 pfoduds I 73 6g l 9. 1254032him-awr 56 SCRUBBER 7 REGENERA ":U' /55 '68 42 an L44 SETTLE}? 59Ox/o/zsR t 74 Ii/6a.:

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' Harry K. Wheeler, Jr: 5 M M Alto J I Patented Sept. 14, 1943 POWERRECOVERY rzan SOLIDS FROM CATALYTIC cou- VERSION SYSTEMS EMPLOYINGFLUID- Harry K. Wheeler, Jr., Chicago, Ill., auignor to Standard OilCompany, Chicago, 11]., a corporation of Indiana Original applicationMarch 29, 1945, Serial No.

Divided and this application January 15, 1948, Serial No. 2,434

i 4 Claims. (Cl. 196-52) This invention relates to catalytic conversionsystems employing fluidized solid-s and it pertains more particularly toimproved methods and means for recovering catalyst solids from ga-siformstreams and for more effectively utilizing the potential energy ofsaidstreams. This is a division of a copending application Serial585,490 flied jointly with Robert J. Hengstebeck on March 29, 1945,wherein improvements in solids separation are claimed. The claims inthis case are directed to a combination of steps which include removalofsolids from hot regeneration gases and the subsequent utilization of thehot gases, which may have their energy content even further enhanced,for supplying motive power.

The invention is applicable to any catalytic conversion system whereinsolid catalyst material spent catalyst by providing improved methods.feed stock (U. s. Patents 2,273,07545).

and means for washing and displacing cokeforming oil from the settledcatalyst particles and returning said particles in heavy virgin oilsuspension with no substantial amounts of heavy cracked materials.

It has been found that catalyst particles may be recovered fromregeneration gases by countercurrent scrubbing with at least a portionof the In such a process however a certain amount of the valuable feedstock is lost by vaporization and there of small particle size ishandled as a fluidized mass and continuously cycled from a conversionzone to a, regeneration zone and thence back to the conversion zone. Insuch a system certain amounts of finely divided solids are unavoidablycarried overhead with eiiluent ga-siform streams from the reaction zoneand the regeneration zone respectively. An object of the invention is toprovide improved methods and means for recovering such solids from suchstreams at minimum expense and with maximum utilization of the potentialenergy of said streams and maximum conservation of valuable chargingstock and product components.

In catalytic cracking system-s employing fluidized solids as catalystmaterials it has been the practice to recover solids from the eilluentproduct stream in a scrubbing zone which forms the lower part of aninitial fractionating zone, a portion of the solids-containing bottomsfrom the scrubbing zone being recycled through a cooler to the upperpart of the scrubbing zone above the hot product inlet. An object of theinvention is to avoid the recycle of solids-containing liquids and toemploy a substantially solids-free oil as a cooling and scrubbing agentin the scrubbing zone or zones.

That portion of the solids-containing liquid which has been withdrawnfrom the base of the scrubbing zone has heretofore been returned withcharging stock to the catalytic cracking conversion zone. It was foundhowever that the return of this material leads to the deposition ofunduly large amounts of coke on the catalyst in the conversion zone andthat the best practice is to settle these solids from the withdrawnsolids-containing liquid and to avoid the return of the bulk of theliquid to the conversion zone; An object of the invention is to improvethe process of returning tion gas.

is a tendency toward oxidation of valuable charge components by residualoxygen in the regenera- An object of the invention is to provide animproved method and mean-s for recovering solids from regeneration gasesand for avoiding the necessity of any contacting of hot regenerationgases with incoming charging stock. A further object is to accomplishthe removal of solids from regeneration gases with minimum capitalinvestment and minimum operating costs.

An important object of the invention is to utilize the potential energyof gaseous streams from fluidized solids systems more effectively thansuch potential energy has heretofore been utilized. A further object isto provide a method and means for enhancing the potential energy contentof a regeneration gas stream simultaneously with the removal of solidstherefrom and for subsequently recovering at least a substantial portionof the enhanced energy content thereof. Other objects will be apparentas the detaileddescription of the invention proceeds. 1

The invention will be described as applied to the catalytic cracking ofgas oils or reduced crudes to produce motor fuel but it should beunderstood that the invention is also applicable to other hydrocarbonconversion processes such as retreating, reforming, hydroforming,aromatization, hydrogenation, dehydrogenation, desulfurization,

- etc., and in fact to fluidized solids conversion steam or preheatingincoming charging stock. The scrubbing oil for both the product streamsand the regeneration gas streams may be substantially free from solidsthus improving the solids separation step as well as minimizing erosionon transfer lines, pipes, heat exchangers, etc. The residual product oilwhich serves as a scrubbing oil for catalyst removal is not onlyefl'ectiveiy kept out of the charge stream but it is utilized forrecovering catalyst from regeneration gases and enriching saidregeneration gases to form a hot combustible stream which'may be burnedwith preheated air to supply motive power for a turbine or otherindustrial use.

The invention will be more clearly understood from the followingdetailed description of a specific example and from the accompanyingdrawings which form a part of this specification and in which:

Figure 1 is a schematic flow diagram of the improved catalyst and powerrecovery system and,

Figure 2 is a vertical section through the combined settler-steamgenerator.

Referring to Figure 1, a charging stock such, for example as a gas oilor reduced crude, is introduced through line l and transfer line H tothe base of reactor i2. Hot regenerated catalyst from regenerator I3 isintroduced by standpipe i4 into transfer line I I in amounts sufficientto effect the desired conversion and to supply at least a considerableportion of the heat required therefor.-

- ployed, the contained heat of the catalyst may supply not only theheat of conversion but all or a substantial part of the heat ofvaporizationof the charging stock. The charging stock may however besuitably preheated and if desired it may be vaporized and preheated tosubstantially conversion temperature before it picks up the catalystfrom the base of standpipe I4. The flow of catalyst through standpipe l4maybe regulated by valve i5 and the catalyst in the standpipe may bemaintained in aerated liquid-like condition by the introduction ofaeration gas through line It.

The suspension of regenerated catalyst in incoming charging stock isdistributed in reactor I2 by means of grid l1 and a vertical gas orvapor velocity in the reactor is maintained in the approximate range ofabout 1 to 3 feet per second so that a suspended dense turbulent phaseor catalyst is maintained in the reactor, which dense phase issuperimposed by a light dispersed phase. Catalyst may be knocked backfrom the light phase to the dense phase by means of cyclone sep--arators l8 or other known means, the gasiform product being withdrawnoverhead through line i9 to the base of scrubber 20 which forms thelower' part of fractionating tower 2|. Reactor l2 may be operated underany desired conversion conditions, conversion temperatures usually beingwithin the approximate range of 800 to 1000 F. for example about 925 F.and the pressure being within the approximate range of about atmosphericto about 10 atmospheres. The weight ratio or catalyst-to-oil in thesuspension introduced into the reactor may be'within the approximaterange of 1:1 to 30:1, the residence time of the catalyst in the reactormay be within the approximate range of about 2 to 200 minutes and theweight space velocity will be within the approximate range or .2 topounds of charging stock introduced per hour per pound of catalystmaintained in the reactor.

- Catalyst is withdrawn directly from the dense phase in reactor I2 intostripping zone 22 wherein it is stripped with steam or other strippinggas introduced through line 23. The stripped catalyst passes downwardlyin standpipe 24, is maintained in fluent liquid-like form therein byaeration gas introduced through line 25 and is dispersed from the baseoi the standpipe through valve 28 into conduit 21 wherein the catalystis suspended in air introduced from line 28 and the suspension iscarried to the base of regenerator ii.

The suspension is distributed in regenerator ll by means of grid 29 andupflowing gas velocities of about 1 to 3 feet per second are employed tomaintain the catalyst in the regenerator as a suspended dense turbulentphase superimposed by a light dispersed phase. A portion of the densephase catalyst may be recycled through standpipe 30 and cooler 3i tomaintain regeneration temperature within desired limits. Cycloneseparators 32 or other suitable means may be employed to knock backcatalyst from the dilute phase to the dense phase. Hot regenerationgases are removed from the regenerator by line 33. The system thus, fardescribed is conventional fluid type catalytic cracking. My invention isnot limited to this particular system but is applicable to any fluidizedsolids conversion system that presents the problem of recovery solidsand heat or energy from effluent gasii'orm streams. More detaileddescriptions of such systems and or the catalyst conditions employedtherein are set forth in U. S. Patents 2,337,684 and 2,341,193

and in numerous copending applications.

For recovering solids froma product stream a substantially solids-freenon-volatile oil may be cooled in heat exchanger 34 (although suchcooling, 1. e. the use of such heat exchanger is not always necessary)and introduced through line 35 at the upper part of scrubber 20 whichmay be provided with suitable baflles 36. Oil introduced through line 35effects the condensation of the highest boiling components of theproduct stream and simultaneously scrubs the solids out of said stream.Components of the gas oil boiling range together with lower boilingcomponents pass upwardly from the scrubbing section 20 to the rectifyingor fractionating' portion of tower 2i from which a, heavy gas oil streammay be withdrawn through line 31 and a light gas oil stream through line38. Gasoline boiling range components, steam and normally gaseousmaterials are taken overhead through line 39 for fractionation andrecovery in the usual manner.

The hot scrubbing oil, condensate. and suspended solids .are withdrawnfrom the base of scrubber 20 through line 40. A heat exchanger forincoming charging stock or waste heat boiler 4i may be employed forcooling the withdrawn liquid to a temperature of the order of 300 to 600F. although as described in connection with Figure 2, such cooling maybe effected in the settling zone after solids have been separated fromthe liquids. With valve 42 open, valves 43 and 44 closed, the slurry ofrecovered catalyst solids may be introduced into settling chamber 45.Settled solids may be withdrawn from the inclined bottom of the settlingchamber as a thickened slurry through conduit 45 and returned throughline 4! to charging stock inlet line I. A portion of the charging stockmay be' introduced through line," for facilitating transfer of thesolids. If desired the slurry from line 45 may be introduced by line 49to a washing zone along with a relatively clean non-coke-forming oil andthe catalyst may be settled from such relatively clean oil beforerecycle in .order to eliminate more completely the return ofcoke-forming oil with recycled catalyst. I

Substantially solids-free oil is withdrawn from settler 45 by line 50and at least a substantial part of this withdrawn oil is introduced bypump and line 35 backto the upper part of scrubbing zone 20. Theremainder of the solids-free oil may be withdrawn from the systemthrough line 52 and it is preferably introduced by pump 53 and line 54to the upper partof scrubber 55 which may be provided with suitablebailles or other means for securing effective gas-liquid contact.Regeneration gas from line 33 is introduced at the base of scrubber 55.When the potential energy in the regeneration gas stream is to beutilized for driving a turbine this stream may be introduced at the baseof scrubber 55 directly from the top of the regenerator and Without anyappreciable cooling. However, I may employ a waste heat boiler 56 and Imay by-pass all or a sufficient part of the regeneration gas throughsaid waste heat boiler, materially reduce the temperature of gasesentering scrubber 55 and generate high pressure steam. The temperatureof the gases entering the base of scrubber 55 is preferably within therange of about 600 to 1200 F. and for example may be about 900 F. to1000 F. A sufficient amount of oil is introduced through line 54 toscrub out substantially all of the residual solids 1 contained in theregeneration gases.

The scrubbing liquid with accumulated solids is withdrawn through line51 and heat exchanger or waste heat boiler 58 to settler 59 althoughhere again the waste heat boiler may be built into the settler itself asdescribed in connection with Figure 2. The settled catalyst solids arewithdrawn from the settler through conduit 50 and may be returnedbylines 6| and 41 to line l0 or introduced by lines BI and 62 to settler45. Alterof highly refractory oil being withdrawn through line 85. a

By providing separate settlers 45 and 59 for scrubbers and 55respectively in the manner hereinabove described the product stream isnot contaminated by oils which have been contacted and perhaps partiallyoxidized with the regeneration gas stream. However, when such oxidationpresents no problem I may dispense entirely with settler 45 and pass thesolids-containing oil from line 40 through valve 43 into settler 59. Inthis case a portion of the clear oil from line 54 is returned by pump 51to line 35 for recycle through cooler 34 to the upper part of scrubber20. I maypass the solids-containing liquid from line 40 through valve 44and lines 68 and 54 directly to the upper part of scrubber 55 but suchalternative is open to the objection that the oil introduced at the topof scrubber would contain solids. In the preferred method of operationthe scrubbing oil is substantially freed from solids and hence is moreeflicient for removing solids and less likely to cause erosion, lineplugging, etc.

The hot regeneration gases leaving the top of scrubber 55 may beintroduced by lines 59, I0 and II ,directly to turbine 12 for generatingelectrical energy, driving air compressors or otherwise utilizingpotential energy of this gas stream. The removal of solids in scrubber55 prevents the erosion of turbine blades and parts.

when spherical catalyst particles are employed and such particles areubstantially quantitatively removed from generation gases by cyclones 52or other separation means'the use of scrubber 55 may be unnecessary andthe hot regeneration gases may be introduced directly to the turbinethrough lines 33,1169," and II.

When scrubber 55 is employed and operated at a high temperature upwardsfor example of 900 F., part of the oil introduced through line 54 willbe vaporized and carried along with the gases leaving the scrubberthrough line 69. To utilize the potential energy of this gas stream Imaypass it through line 14 through one of the oxidizing chambers 15 and15a (into which an air stream can be introduced through line 15 ifadditional oxygen is necessary) for effecting combustion of thehydrocarbon vapors in th gas stream that were picked up in the scrubberand for materially increasing the temperature of the gases introducedthrough line H to turbine I2. The off gases from the turbine may bepassed through line 11 through exchanger 18 and the incoming air streamfrom line I! may be passed through this exchanger in order to preheatthe air introduced through line 16 to the oxidizing chambers. Oxidizingchamber 15 may be open vessels of the type commonly known as flue gasgenerators or they may be packed with any known type of oxidationcatalyst material for insuring substantially comper square inch (gaugepressure).

plete combustion. In the manner above described I may materially augmentthe potential energy available for utilization by the turbine. Theenergy of the stream may be further augmented by the introduction oftail gases from the product recovery system through line III with acorresponding increase in the amount of air introduced through line 15.

By operating the entire system at superatmospheric pressure I cangreatly increase the amount of power obtainable from the regenerationgases by the turbine and at the-same time effect savings in equipmentcosts by employing a smaller reactor, regenerator, etc. The catalystrecovery system is just as efficient at low pressures as at highpressures and may be employed very advantageously in systems wherein thetop pressure in the reactor is of the order of 5 to 10 poundsRegenerator pressure is closely tied to reactor pressure because of thefluids flow system between reactor and regenerator. However, by placingthe reactor at a considerably higher level than the regenerator,-

upper boiler section through conduit 84 and this section may be providedwith'staggered baiiies 85 between the water inlet and steam outlet 88.The incoming slurry from line 51a passes under the boiler section and isprevented from short circuiting the boiler by extensions 81 of theboiler walls which are secured to the end wall oi. settler 58a. Solidssettle out of the slurry in the lower part 01' settler 59a where thetemperature of the oil is highest and its viscosity is therefore at aminimum. The solids-free voil then passes through tubes 82 of the'wasteheat boiler for generating steam which may be employed as process steamin the system or for supplying heat or for driving compressors orgenerators. Catalyst solids are removed through conduits 80a and theclear cooled oil streams are withdrawn through lines 84a. Instead ofgenerating steam in section 8| I may useit to preheat incoming chargingstock or for heating any other fluids.

While I have disclosed a specific system for recovering solids andenergy from gasiform solids leaving the fluidized solids treating systemit should be understood that the invention is not limitedto the specificarrangements or detailed operations hereinabove set iorth'since variousalternative arrangements and operating conditions will be apparent fromthe above description to those skilled in the art.

I claim:

1. In a catalytic conversion system wherein solid catalyst material ofsmall particle sizeis handled as a fluidized mass and continuouslycycled from a conversion zone to a regeneration zone and thence backto aconversion zone and :wherein a hot regeneration gas stream containingresidual solid particles is discharged from the regeneration zone atsuperatmospheric pressure, the method of operation which comprisesscrubbing said residual solids from said stream with a hot non-volatilehydrocarbon liquid in a scrubbing zone which is at a temperature of atleast about 900 F. whereby solids are removed from said stream withoutcooling it below such temperature and impelling a generator of motivepower with said stream from which residual solids have thus beenremoved.

2. In a catalytic conversion system wherein solid catalyst material ofsmall particle size is handled as a fluidized mass and continuouslycycled from a conversion zone to a regeneration zone and thence back toa conversion zone and wherein a hot regeneration gas stream containingresidual solid particles is discharged from the regeneration zone atsuperatmospheric pressure, the method of operation which comprisesscrubbing said stream with a 'high boiling hydrocarbon oil in ascrubbing zone which is at a temperature of at least about 900 F. underconditions for effecting removal of residual soiids from the stream andenrichment of said stream with hydrocarbon vapors, eflfecting combustionof said hydrocarbon vapors in said stream to increase the temperaturethereof and impelling a generator of motive power with said stream fromwhich said solids have been removed and the temperature of which hasthus been increased by said combustion.

3. In a catalytic conversion system wherein solid catalyst material ofsmall particle size is handled as a fluidized mass and continuouslycycled from a conversion zone to a regeneration zone and thence vback tothe conversion zone and wherein a hot regeneration gas stream containingresidual solid particles is discharged from the regeneration zone atsuperatmospheric pressure and at a temperature higher than 900 F., themethod of operation. which comprises separating from products leavingthe conversion zone a residual fraction comprising the highest boilinghydrocarbon product components, scrubbing said residual solid particlesfrom said not regeneration gas stream with said residual traction in ascrubbing zone at a temperature of about 900 F. whereby solids areremoved from said stream at said temperature and impelling a generatorof motive power with said hot stream from which residual solids havethus been removed.

4. The method of claim 3 which includes the step of effecting combustionof hydrocarbon vapors which become associated with said stream in thescrubbing step before impelling such generator of motive power with saidstream.

HARRY K. WHEELER, JR.

REFERENCES CI'l ED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

